Slurry hydroprocessing process

ABSTRACT

A novel slurry hydrotreating process is described which employs a hydrotreating catalyst of small particle size having a quantity of catalyst sites in excess of those required for reaction and/or adsorption of nitrogen compounds in the petroleum or synfuel feed being treated. The excess catalyst sites can therefore in effect be contacted with a low nitrogen or essentially zero nitrogen feed, allowing rapid hydrogenation of aromatics at low temperatures where equilibrium is favored. In a further aspect of the invention, the catalyst which contains adsorbed nitrogen is activated by high temperature denitrogenation.

BACKGROUND OF THE INVENTION

This invention relates to the use of certain small particle catalysts ina slurry hydrotreating process for the removal of sulfur and nitrogencompounds and the hydrogenation of aromatic molecules present in lightfossil fuels such as petroleum mid-distillates.

A well known application for a hydrotreating process in a refinery isthe treatment of the light catalytic cracker cycle oil (LCCO) productfrom a catalytic cracker. The term LCCO may refer to furnace oil, dieseloil, or mixtures thereof, as distinguished from the other main productstreams of the catalytic cracker, typically the gasoline and gas productstream and the heavy fuel oils product stream.

The LCCO product is relatively high in aromatic content and increasinglyso as a result of the catalytic cracker being operated at a highertemperature in order to produce more gasoline. In other words, a highergasoline conversion in the catalytic cracker is being obtained at theexpense of a more aromatic LCCO product than in the past. However, theLCCO product is generally of less demand and consequently of less valuethan the gasoline product, and the problem of disposing of the LCCOproduct has arisen. One option is to hydrogenate the aromatics in theLCCO product and sell it as heating oil. However, this option may not beviable when the market for heating oil is insufficient. A second optionis to make the LCCO product suitable for diesel oil stock. However,there already exists a stringent sulfur limit for diesel fuel and thereis likely to be a stringent aromatics limit because of the effect ofaromatics on soot formation. A third option for the LCCO product is torecycle it back to the catalytic cracker for further conversion, butsince coke making is to be avoided, it is necessary to hydrogenate theLCCO before recycling.

The petroleum industry therefore hydrotreats LCCO's such as furnace oilor diesel oil, whether to upgrade the same for a final product or toupgrade them for recycle to the catalytic cracker.

Hydrotreating is a process wherein the quality of a petroleum feedstockis improved by treating the same with hydrogen in the presence of ahydrotreating catalyst. Various types of reactions may occur duringhydrotreating. In one type of reaction, the mercaptans, disulfides,thiophenes, benzothiophenes and dibenzothiophenes are desulfurized. Thethiophenes, mercaptans and disulfides are representative of a highpercentage of the total sulfur in lighter naphthas. Benzothiophenes anddibenzothiophenes appear as the predominant sulfur forms in heavierfeeds such as LCCO and VGO. Hydrotreating also removes nitrogen fromvarious nitrogen compounds such as carbazoles, pyridines, and acridines.Hydrotreating can also hydrogenate aromatic compounds, existing ascondensed aromatic ring structures with 1 to 3 or more aromatic ringssuch as benzene, alkyl substituted benzene, naphthalene, andphenanthrene.

The most common hydrotreating process utilizes a fixed bed hydrotreater.A fixed bed system, however, has several disadvantages or inherentlimitations. At relatively low temperatures and employing a conventionalcatalyst, a fixed bed system is characterized by relatively low reactionrates for the hydrogenation of multi-ring aromatics and the removal ofnitrogen in the material being treated. On the other hand, at relativelyhigher temperatures, a fixed bed system suffers from equilibrium limitswith respect to the degree of aromatics hydrogenation.

Another limitation of a fixed bed system is the difficulty incontrolling the temperature profile in the catalyst bed. As a result,exothermic reactions may lead to undesirably higher temperatures indownstream beds and consequently an unfavorable equilibrium. Still afurther limitation of a fixed bed system is that a high pressure dropmay be encountered, when employing small particle catalysts to reducediffusion limits. Finally, a fixed bed system suffers from catalystdeactivation, which requires period shutdown of the reactor.

Hydrotreating processes utilizing a slurry of dispersed catalysts inadmixture with a hydrocarbon oil are generally known. For example, U.S.Pat. No. 4,557,821 to Lopez et al discloses hydrotreating a heavy oilemploying a circulating slurry catalyst. Other patents disclosing slurryhydrotreating include U.S. Pat. Nos. 3,297,563; 2,912,375; and2,700,015.

Conventional hydrotreating processes utilizing a slurry system avoidsome of the limits of a fixed bed system. In a slurry system, it ispossible to use small particle catalysts without a high pressure drop.Further, it is possible to replace deactivated catalyst "on-stream" withfresh reactivated catalyst. However, the conventional slurryhydrotreating process at high reactor temperatures still is limited withrespect to the overall degree of aromatics hydrogenation. At lowtemperatures, it is possible to obtain better heat transfer and mixingand to control any temperature rise so as to maintain a favorableequilibrium level. However, the overall reaction rates in theconventional slurry process at low temperatures are relatively poor.Poor reaction rates are believed to result from poisoning of thecatalyst by organic nitrogen molecules in the feed being treated. Suchcompounds adsorb on the catalyst and tie up the sites needed forhydrotreating reactions.

The present process overcomes the limits and disadvantages ofconventional hydrotreating by employing certain finely dividedhydrotreating catalysts in slurry form to contact the feed. According tothe present invention, sufficient catalyst sites are packed into theslurry such that most of the nitrogen molecules can be titrated, that isabsorbed, on the slurry catalyst without adversely affecting thehydrotreating process. Excess catalyst sites are present such that sitesfree of nitrogen are capable of hydrogenating the aromatics in a low oressentially nitrogen free feed.

The hydrotreating process of the present invention has the advantagethat it can occur even at low temperatures, for example 650° F to 700°F, where equilibrium is favorable. In a further aspect of the presentinvention, any nitrogen is subsequently removed from the catalyst in ahigh temperature reactivation step before the catalyst recontacts freshfeed.

BRIEF DESCRIPTION OF THE INVENTION

The present invention teaches a method of maximizing hydrogenationreaction rates of light fossil fuel feedstocks in a hydrotreatingprocess while avoiding reaction equilibrium limits. These and otherobjects are accomplished according to our invention, which comprisespassing the feedstock in admixture with a hydrogen containing gasthrough a hydrotreating zone in contact with a hydrotreating catalyst inslurry form such that substantial nitrogen removal,hydrodesulfurization, and aromatics hydrogenation is carried out. Thecatalyst particles are micron to 1/8 inch in average diameter and arecharacterized by an index, referred to as the excess catalyst index(ECI), equal to a value in the range of about 5 to 125, preferably about30 to 90, according to the following formula: ##EQU1## wherein W_(f) isthe weight of the feed in lbs/hr, N_(c) is the concentration of thenitrogen in ppm, W_(s) is the rate of catalyst addition in lbs/hr andM_(c) is the concentration of the metals on the catalyst in weightpercent.

BRIEF DESCRIPTION OF THE DRAWINGS

The process of the invention will be more clearly understood uponreference to the detailed discussion below upon reference to thedrawings wherein:

FIG. 1 shows a schematic diagram of one embodiment of a processaccording to this invention wherein an LCCO feed stream is hydrotreated;

FIG. 2 contains a graph illustrating aromatics hydrogenation in a slurryhydrotreating process according to the present invention;

FIG. 3 contains a graph illustrating sulfur removal in a slurryhydrotreating process according to the present invention; and

FIG. 4 contains a graph illustrating nitrogen removal in a slurryhydrotreating process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Applicants' process is directed to a hydrotreating process using ahydrotreating catalyst of small particle size having a quantity of sitesin excess of those required for reaction and/or adsorption of most ifnot all of the nitrogen compounds present when the catalyst is contactedwith petroleum or synfuel feedstocks. In effect, the feedstock assumes alow nitrogen or essentially zero nitrogen character such that it can becontacted by the excess catalyst sites, allowing rapid hydrogenation ofaromatics at low temperatures where equilibrium is favored. In a furtheraspect of the invention, it has been found that the catalyst, whichcontains adsorbed nitrogen from the hydrotreating step can beadvantageously reactivated by high temperature denitrogenation before itis recontacted with high nitrogen fresh feed.

The slurry hydrotreating process of this invention can be used to treatvarious feeds including mid-distillates from fossil fuels such as lightcatalytic cycle cracking oils (LCCO). Distillates derived frompetroleum, coal, bitumen, tar sands, or shale oil are likewise suitablefeeds. On the other hand, the present process is not useful for treatingheavy catalytic cracking cycle oils (HCCO), coker gas oils, vacuum gasoils (VGO) and heavier resids, which contain several percent 3+ ringaromatics, particularly large asphaltenic molecules. When treatingheavier resids, excess catalyst sites are not obtainable, andreactivation of the catalyst by high temperature denitrogenation is notfeasible.

Suitable feeds for processing according to the present invention includethose distillate fractions which are distilled in the range of 350 to750° F., preferably in the 400 to 700° F. range, and most preferably inthe 430 to 650° F. range. Above 750° F., the feed is generally tooheavy. Below 300° F., the feed is generally too light since substantialvapor is present. In general, the nitrogen content of the feed issuitably in the range of 350 to 1000 ppm, preferably 350 to 750 ppm. Theconcentration of polar aromatics, as measured by HPLC, is suitably lessthan 2 percent and the concarbon is suitably less than one-half percent.In terms of total aromatics, the percent is suitably higher, up to 50weight percent or even greater.

Suitable catalysts for use in the present process are well known in theart and include, but are not limited to, molybdenum (Mo) sulfides,mixtures of transition metal sulfides such as Ni, Mo, Co, Fe, W, Mn, andthe like. Typical catalysts include NiMo, CoMo, or CoNiMo combinations.In general sulfides of Group VII metals are suitable. (The PeriodicTable of Elements referred to herein is given in Handbook of Chemistryand Physics, published by the Chemical Rubber Publishing Company,Cleveland, OH, 45the Edition, 1964.) These catalyst materials can beunsupported or supported on inorganic oxides such as alumina, silica,titania, silica alumina, silica magnesia and mixtures thereof. Zeolitessuch as USY or acid micro supports such as aluminated CAB-0-SIL can besuitably composited with these supports. Catalysts formed in-situ fromsoluble precursors such as Ni and Mo naphthenate or salts ofphosphomolybdic acids are suitable.

In general the catalyst material may range in diameter from 1 μ to 1/8inch. Preferably, the catalyst particles are 1 to 400 μ in diameter sothat intra particle diffusion limitations are minimized or eliminatedduring hydrotreating.

In supported catalysts, transition metals such as Mo are suitablypresent at a weight percent of 5 to 30%, preferably 10 to 20%. Promotermetals such as Ni and/or Co are typically present in the amount of 1 to5%. The surface area is suitably about 80 to 400 m^(2/) g, preferably150 to 300 m^(2/) g.

Methods of preparing the catalyst are well known. Typically, the aluminasupport is formed by precipitating alumina in hydrous form from amixture of acidic reagents in an alkaline aqueous aluminate solution. Aslurry is formed upon precipitation of the hydrous alumina. This slurryis concentrated and generally spray dried to provide a catalyst supportor carrier. The carrier is then impregnated with catalytic metals andsubsequently calcined. For example, suitable reagents and conditions forpreparing the support are disclosed in U.S. Pat. Nos. 3,770,617 and3,531,398, herein incorporated by reference. To prepare catalysts up to200 microns in average diameter, spray drying is generally the preferredmethod of obtaining the final form of the catalyst particle. To preparelarger size catalysts, for example about 1/32 to 1/8 inch in averagediameter, extruding is commonly used to form the catalyst. To producecatalyst particles in the range of 200 μ to 1/32 inch, the oil dropmethod is preferred. The well known oil drop method comprises forming analumina hydrosol by any of the teachings taught in the prior art, forexample by reacting aluminum with hydrochloric acid, combining thehydrosol with a suitable gelling agent and dropping the resultantmixture into an oil bath until hydrogel spheres are formed. The spheresare then continuously withdrawn from the oil bath, washed, dried, andcalcined. This treatment converts the alumina hydrogel to correspondingcrystalline gamma alumina particles. They are then impregnated withcatalytic metals as with spray dried particles. See for example, U.S.Pat. Nos. 3,745,112 and 2,620,314.

The catalyst used in the present process must have the necessary numberof reaction sites. It has been found that the number of catalyst sitesis related, as a practical matter, to a parameter defined as the "excesscatalyst index" or ECI. The value of this index must equal a number inthe range of about 5 to 125, preferably about 30 to 90. The ECIparameter, which determines the operating limits for a given catalystand feed systems is defined as follows: ##EQU2## wherein W_(f) is theweight of the feed in 1lbs/hr, N_(c) is the concentration of thenitrogen in ppm, W_(s) is the rate of catalyst addition in lbs/hr andM_(c) is the concentration of the metals on the catalyst in weightpercent.

The catalyst is used in the hydrotreating step in the form of a slurry.The catalyst concentration is suitably about 10 to 40 percent by weight,preferably about 15 to 30 percent.

In the hydrotreating process, the hydrodesulfurization,hydrodenitrogenation and aromatic hydrogenation reactions are a functionof the total number of active sites on the catalyst. On a supportedcatalyst, the number of sites is proportional to the active metalscontent and the dispersion of those metals on the support. The sulfur,nitrogen and aromatic molecules present in the feed must absorb on thesesites for reaction to occur. The nitrogen molecules absorb on thesesites more strongly than other molecules in an LCCO or comparable feedand consequently such molecules are most difficult to react off. Byproviding excess catalyst sites, the nitrogen molecules in the feed canbe titrated or removed from the feed, leaving excess sites available forhydrodesulfurization and aromatics hydrogenation. The aromaticshydrogenation reaction is especially fast on these free catalyst sites.The term (W_(s) M_(c)) in the ECI index is a measure of the total sitesavailable. The term (W_(f) N_(c)) is a measure of the molecules oforganic nitrogen in the feed. The ratio of these two terms provides anindex which effectively measures the number of excess sites availablefor the desired reactions. According to the present process, thenitrogen remaining absorbed on the catalyst can be removed by separatingthe catalyst from the product and then exposing the catalyst tosufficiently severe conditions, particularly higher temperatures, suchthat the nitrogen is removed by hydrodenitrogenation.

Referring now to FIG. 1, a feed stream 1, by way of example a lightcatalytic cracker cycle oil (LCCO), is introduced into a slurryhydrotreating reactor 2 designated R-1. Before being passed to thehydrotreating reactor, the feed is mixed with a hydrogen containing gasstream 6 and heated to a reaction temperature in a furnace or preheater3. Alternatively, the hydrogen gas in stream 6 can be introduceddirectly into the hydrotreating reactor 2. The reactor contains aslurried catalyst having, by way of example, a particle diameter of 10to 200 μ. Recycle of the reactor effluent via a pump is optional toprovide mixing within the reactor. Alternatively, the feed may enterthrough the bottom of the reactor and bubble up through an ebulating orfluidized bed.

The process conditions in the hydrotreating reactor 2 depend on theparticular feed being treated. In general, the hydrotreater is suitablyat a temperature of about 550 to 700° F., preferably about 600 to 650°F. and at a pressure of about 300 to 1200 psig, preferably about 500 to800 psig. The hydrogen treat gas rate is suitably about 200 to 2000SCF/B (standard cubic feet per barrel), preferably about 500 to 1500SCF/B. The space velocity or holding time (W_(R) /W_(f) where W_(R) isthe catalyst held up in the hydrotreating reactor in lbs and W_(f) isthe rate of feed thereto in lbs/hr) is suitably about 0.5 to 4 hours andpreferably about 1 to 2 hours.

The effluent from the hydrotreating reactor 2 is passed via stream 4through a cooler 5 and introduced into a gas-liquid separator ordisengaging means 7 where tho hydrogen gas along with ammonia andhydrogen sulfide by-products from the hydrotreating reactions may beseparated from the liquid effluent and recycled via stream 8 andcompressor 9 back for reuse in the hydrogen stream 6. The recycled gasis usually passed through a scrubber 10 to remove hydrogen sulfide andammonia. This is usually recommended because of the inhibiting effect ofsuch gases on the kinetics of hydrotreating and also to reduce corrosionin the recycle circuit. Fresh make-up hydrogen is suitably introducedvia stream 11 into the recycle circuit. The liquid effluent from thegas-liquid separator 7 enters via stream 12 a solids separator 14, whichmay be a filter, vacuum flash, centrifuge or the like, in order todivide the hydrotreating reactor effluent into a catalyst stream 15 anda product stream 16. The product in stream 16 is suitable for blendingin the diesel pool and contains less than 5 ppm nitrogen and less than20 wt. % aromatics. The product is typically reduced in sulfur as well.In many cases, the product is given a light caustic wash to assurecomplete removal of H₂ S. Small quantities of H₂ S, if left in theproduct, will tend to oxidize to free sulfur upon exposure to the air,and may cause the product to exceed pollution or corrosionspecifications.

In a further aspect of the present invention, the catalyst isreactivated by means of high temperature denitrogenation. Referringagain to FIG. 1, the catalyst stream 15 from the solids separator 14,comprises typically about 50 weight percent catalyst. A suitable rangeis about 30 to 60 percent. The catalyst material is transported viastream 15 and after preheating introduced into reactivator 20,designated R-2, to react off most of the nitrogen molecules which occupycatalyst sites. Recycle hydrogen 6 is co-fed into the reactivator 20.The reactivator 20 yields a reactivated catalyst stream 21 for recycleback to the hydrotreating reactor 2. Fresh make-up catalyst is suitablyintroduced via stream 22 into the catalyst recycle stream 21 and spentcatalyst may be removed via stream 17 from catalyst stream 15.

The reactivator 20 is suitably maintained at a temperature of about 700to 800° F., preferably about 725 to 775° F., and at a pressure of about500 to 1500 psig, preferably about 700 to 1000 psig. The hydrogen treatgas rate is suitably about 200 to 1500 SCF/B, preferably about 500 to1000 SCF/B. The holding time is suitably about 0.5 to 2 hours,preferably about 1 to 1.5 hours (W_(R') /W_(f) ' where W_(R), is thecatalyst hold up in the reactivator in lbs and W_(f) is the rate of feedthereto in lbs/hr).

EXAMPLE 1

A continuous slurry process was simulated using a batch autoclave. Theautoclave was a 300 cc reactor equipped with an air driven stirreroperated at 450 RPM and sufficient internal baffling to ensure goodmixing. The unit was also equipped with (1) a system to pressure thecatalyst into the autoclave, (2) lines for continuous addition andremoval of gas and (3) an internal line having a fritted disc to removeliquid for analysis. A commercially available hydrotreating catalyst wasused having the following properties:

    ______________________________________                                        NiO, wt %         3.8                                                         MoO.sub.3, wt %   19.4                                                        Surface Area, m.sup.2 /gm                                                                       175                                                         Pore Volume, cc/gm                                                                              0.38                                                        ______________________________________                                    

The catalyst was first crushed to 65-100 mesh and sulfided in acontinuous flow of 1.5 liters/hr of 10% hydrogen sulfide in hydrogen at350° C. The catalyst (5 gm) was slurried in a small quantity of the LCCOfeed having the following properties:

    ______________________________________                                        Sulfur, wt %       1.27                                                       Nitrogen, ppm      772                                                        Saturates, wt %    19.7                                                       1-ring Aromatics, wt %                                                                           22.2                                                       2-ring Aromatics, wt %                                                                           42.0                                                       3-ring Aromatics, wt %                                                                           16.1                                                       ______________________________________                                    

The slurry was placed in the catalyst addition hopper. Sufficient LCCOfeed was added to the autoclave reactor to make a slurry containing 6wt. % catalyst when the two were combined. The reactor was flushed withnitrogen and then hydrogen. The pressure on the reactor was increased to750 psig with a continuous flow of hydrogen at 1.5-2.0 liters/hr whichwas used to purge from the reactor hydrogen sulfide generated during thehydrotreating step. The leaving gas was cooled to condense any liquidand returned to the reactor. The temperature of the autoclave wasincreased to 343° C. and the stirrer turned on at 450 RPM. Once thereactor had lined out at these conditions the catalyst in the catalystaddition hopper was pressured into the autoclave. Samples were withdrawnfrom the reactor at intervals and analyzed to determine the sulfur,nitrogen and aromatics/saturates content.

The sulfur and nitrogen content of the products was plotted in terms of% sulfur (FIG. 3) and % nitrogen (FIG. 4) remaining as a function of thecorrected holding time which takes into consideration the amount ofcatalyst holdup in the reactor. In FIGS. 3 and 4, the symbols have thefollowing definitions: θ' ,is the corrected batch autoclave holding time(hrs); θ is the actual batch autoclave holding time (hrs); W_(R) is theamount of catalyst in the reactor (lbs); and FW is the amount of feed inthe reactor (lbs). The percent nitrogen remaining is equal to 100 timesthe wt. % nitrogen in the product divided by the wt. % nitrogen in thefeed. The percent sulfur removal is defined analogously. The saturatescontent of the products was plotted in FIG. 2. In FIG. 2, the symbolsθ', θ, W_(R) and FW are as defined above and in addition, Se is thethermodynamic equilibrium saturates concentration (wt. %), SP is theproduct saturates concentration (wt. %) and S_(F) is the feed saturatesconcentration (wt. %). In this case the formation of saturates is theslowest hydrogenation rate for hydrotreating catalysts which utilizemolybdenum sulfides as catalysts and best reflect any improvements foundwith new catalysts or processes. Since this reaction is limited bythermodynamic considerations, it was necessary to determine bycorrelation the best equilibrium saturates composition (S_(e)) thatwould yield a straight line as shown on FIG. 2. In each of these casesthe slope of the line is a measure of the reaction rate observed, andthe rate constants derived from this analysis are shown in the followingtabulation:

    ______________________________________                                        Desulfurization (HDS)                                                                            3.5                                                        Denitrogenation (HDN)                                                                            5.4                                                        Saturates Hydro     0.35                                                      ______________________________________                                    

First order kinetics were used to calculate the rate constants for HDNand Saturates Hydro, but HDS employed 1.5 order kinetics.

EXAMPLE 2

The same procedure was followed in this example as was used in Example 1with the exception that sufficient sulfided catalyst (10 gm) was placedin the catalyst addition hopper to provide a 20 wt. % slurry when thecatalyst was added to the feed in the reactor. Once again samples werewithdrawn at intervals and analyzed for sulfur, nitrogen andaromatics/saturates content. The data are shown on FIGS. 2-4 for the 20wt. % slurry case. The equilibrium saturates content (S_(e)) determinedin Example 1 was utilized in this example. The rate constants for thethree reactions were calculated as described in Example 1, and theresults are summarized as follows:

    ______________________________________                                        Desulfurization (HDS)                                                                            4.6                                                        Denitrogenation (HDN)                                                                            12.4                                                       Saturates Hydro    1.6                                                        ______________________________________                                    

It is evident that increasing the concentration of catalyst in theslurry from 6 to 20 wt. % increased the HDS rate 30%, the HDN rate by2.3 fold and the saturates hydrogenation rate by 4.6 fold. In the caseof the HDN rate it is theoretical as to whether the nitrogen was removedfrom the nitrogen containing molecules or simply adsorbed onto theexcess catalyst.

EXAMPLE 3

It is expected that some but not all of the nitrogen containingmolecules would be denitrogenated at the lower temperature (343° C.)used for slurry hydrotreating in Examples 1 and 2, but it would benecessary to first separate the catalyst from the reactor product, heatit to an elevated temperature to perform complete HDN of the adsorbednitrogen containing molecules and then return the reactivated catalystto the slurry reactor for further hydrotreating of the fresh feed.

Denitrogenation data were obtained on a very similar LCCO (1.35 wt. %sulfur, 718 ppm nitrogen) in a fixed bed, continuous flow experimentwith the same commercial hydrotreating catalyst as was used in Examples1 and 2. After sulfiding with 10% hydrogen sulfide in hydrogen atconditions similar to those used in Examples 1 and 2 the catalyst wasused to hydrotreat the LCCO feed at 500 psig, 625° F., 2200 SCF/Bhdyrogen treat gas rate and 0.5 LHSV. The first order HDN rate constantcalculated from these data was 0.85. It is known that the activationenergy of the HDN reaction is 30 kcal/mol which projects a rate constantof 4.0 for the HDN reaction at 705° F. These data show that completeremoval of the nitrogen from the catalyst could be attained, even if allof the nitrogen removed in the low temperature slurry hydrotreater wasonly adsorbed, at 750 psig, 705° F., 500 SCF/B hydrogen treat gas rateand 1.3 hours holding time (W_(R) /W_(F)).

The process of the invention has been described generally and by way ofexample with reference to particular embodiments for purposes of clarityand illustration only. It will be apparent to those skilled in the artfrom the foregoing that various modifications of the process andmaterials disclosed herein can be made without departure from the spiritand scope of the invention.

What is claimed is:
 1. A process for hydrotreating a mid-distillate of ahydrocarbonaceous material, comprising:passing the mid-distillate inadmixture with a hydrogen containing gas through a hydrotreating zone incontact with a hydrotreating catalyst slurry such that substantialnitrogen removal, hydrodesulfurization and aromatics hydrogenation iscarried out and wherein the catalyst comprises catalyst particles 1micron to 1/8 inch in average diameter and are characterized by a valueof about 5 to 125 on an index defined as the excess catalyst index (ECI)according to the following formula: ##EQU3## wherein W_(f) is the weightof the mid-distillate in lbs/hr, N_(c) is the concentration of thenitrogen in distillate in ppm, W_(s) is the rate of catalyst addition tothe hydrotreating zone in lbs/hr and M_(c) is the concentration of themetals on the catalyst in weight percent.
 2. The process of claim 1,wherein the ECI index is equal to a value ranging from about 30 to 60.3. The process of claim 1, wherein the mid-distillate is a product of apetroleum, synfuel, coal, shale oil, bitumen, or tar sand conversionprocess.
 4. The process of claim 1, wherein the mid-distillate is alight catalytic cracking cycle oil.
 5. The process of claim 1, whereinthe mid-distillate boils in the range of 350 to 750° F.
 6. The processof claim 1, wherein the catalyst is comprised of molybdenum sulfide. 7.The process of claim 1, wherein the catalyst further comprises nickeland/or cobalt.
 8. The process of claim 1, wherein the catalyst issupported on an inorganic oxide material.
 9. The process of claimwherein the inorganic oxide material is selected from the groupconsisting of alumina, silica, titania, silica alumina, silica magnesia,and mixtures thereof.
 10. The process of claim 1, wherein the molybdenumis present in the amount of 5 to 30 percent by weight in the catalyst.11. The process of claim 1, wherein the nickel and cobalt is present inthe amount of 1 to 7 percent by weight in the catalyst.
 12. The processof claim 1, wherein the catalyst is 10 μ to 1/8 inch in averagediameter.
 13. The process of claim 11, wherein the catalyst is 10 μ to400 μ in average diameter.
 14. The process of claim 1, wherein thesurface area of the catalyst is 80 to 400 m_(2/) g.
 15. A process forhydrotreating a mid-distillate of a hydrocarbonaceous material,comprising:passing the mid-distillate in admixture with a hydrogencontaining gas through a hydrotreating zone in contact with a slurriedhydrotreating catalyst such that substantial nitrogen removal,hydrodesulfurization and aromatics hydrogenation is carried out whereinthe catalyst comprises particles 1 micron to 1/8 inch in averagediameter and are characterized by a value ranging from about 5 to 125 onan Excess Cathalyst Index (ECI) index defined according to the followingformula: ##EQU4## wherein W_(f) is the weight of the feed to thehydrotreating zone in lbs/hr, N_(c) is the concentration of the nitrogenin the mid-distillate in ppm, W_(s) is the rate of catalyst addition tothe hydrotreating zone in lbs/hr and M_(c) is the concentration of themetals on the catalyst in weight percent; reactivating the catalyst byhigh temperature denitrogenation; and recycling the reactivated catalystto the hydrotreating zone.
 16. The process of claim 15, wherein the ECIindex is equal to a value ranging from about 30 to 90.